With all due respect to Alveda King, I don't know whether her uncle would or would not have worn a hoodie. I do know he understood the importance to the movement of looking professional in public at all times. Nobody deserves to be shot, harassed, followed or intimidated for wearing a hoodie. And if you want to wear a hoodie, wear a hoodie.
The intent of putting King in a hoodie is to illustrate how people(white people) have come to judge people just because they're wearing a hoodie. You shouldn't assume someone has ill intent because of what they wear. That said, people are judged by the close they wear; all people are. If you want to be respected, irrespective of the color of your skin, you need to remember that.